Chemistry question.

Question

Calculate the standard change in Gibbs free energy, ΔG_rxn^∘​, for the given reaction at 25.0^∘C. Consult the table of thermodynamic properties for standard Gibbs free energy of formation values. 

KCl(s)⇌K⁺(aq)+Cl^-(aq) 

ΔG^∘_rxn​=

Determine the concentration of K⁺(aq) if the change in Gibbs free energy, ΔGrxn​, for the reaction, is −8.21 kJ/mol.

[K⁺]= M

Answer 1

From a table of ∆Gºformation:

∆Gºf K⁺(aq) = -283.7 kJ/mol

∆Gºf Cl^-(aq) = -131.2 kJ/mol

∆Gºf KCl(s) = -408.5 kJ/mol

(a) ∆Gºrxn = ∑products - ∑reacdtants

∆Gºrxn = (-283.7 + -131.2) - (-408.5)

∆Gºrxn = -6.40 kJ/mol

(b) ∆Grxn = ∆Gºrxn + RT ln Q

Q = [K⁺][Cl^-] = (x)(x) = x²

-8.21 = -6.40 + (0.008314)(298) ln x²

ln x² = -0.731

x² = 0.482

x = [K⁺] = 0.694 M